The Role of Cardiac MRI in Patients with Troponin-Positive Chest Pain and Unobstructed Coronary Arteries

Abstract

Acute coronary syndrome (ACS) still remains one of the leading causes of mortality and morbidity worldwide. Seven to fifteen percent of patients presenting with ACS have unobstructed coronary artery disease (CAD) on urgent angiography. Patients with ACS and unobstructed coronary arteries represent a clinical dilemma and their diagnosis and management is quite variable in current practice. Cardiovascular magnetic resonance imaging with its unique non-invasive myocardial tissue characterization property has the potential to identify underlying etiologies and reach a final diagnosis. These include acute and chronic myocarditis, embolic/spontaneous recanalization myocardial infarction, and Tako-Tsubo cardiomyopathy, and other conditions. Establishing a final diagnosis has a direct implication on patient’s management and prognosis. In this article, we have reviewed the current evidence on the diagnostic role of cardiac magnetic resonance (CMR) in patients with ACS and unobstructed coronary arteries. We have also highlighted the potential role of CMR as a risk stratification or prognostication tool for this patient population.

Prognostic Role of CMR and Conventional Risk Factors in Myocardial Infarction With Nonobstructed Coronary Arteries

“…(13,18) In our cohort, the most common diagnosis was MI (25%, n=97), closely followed by myocarditis (25%, n=96) and cardiomyopathy (25%). However, the literature suggests myocarditis to be much more common than MI (10)(11)(12)(13)15), contrary to our result. The mean age in our study was much higher compared to the other studies on MINOCA which may have contributed to the higher prevalence of MI.…”

“…(3) (9) Confirmation or exclusion of myocardial infarction (MI) by CMR facilitates tailoring of medical therapy, ensuring appropriate long-term secondary prevention and modification of risk, and also minimizing exposure to anti-platelet therapy and the associated bleeding risks for those with a non-coronary aetiology for the MINOCA presentation. (10). Few previous studies have shown that CMR can identify the underlying diagnosis, most commonly: acute/chronic myocarditis, acute MI with spontaneous recanalization/embolus, stress cardiomyopathy (Takotsubo) or other cardiomyopathies.…”

Chest pain: coronary CT in the ER

“…53,54 Moreover, from 7 to 15% of patients presenting with ACS had unobstructed coronaries on urgent invasive or non-invasive angiography representing a clinical dilemma, as the underlying diagnosis is variable and often unclear. 55 In this scenario, CMRI may play a consistent role in differential diagnoses of important mimickers of ACS. By using a multiparametric protocol, MRI may be particularly useful in determining the diagnosis and differentiate ischaemic from non-ischaemic causes, thereby guiding patient management.…”

“…These include in most of the cases (.95%) myocarditis, embolic/spontaneous recanalization myocardial infarction and Tako-Tsubo cardiomyopathy. 3,55 Since some abnormalities such as myocardial oedema/inflammation may be reversible and resolve with time, MRI scan performed at the time of acute presentation is more sensitive for diagnosis.…”

“…89 Another important concept is that in approximately 7-15% of all ACS events, no significant stenosis is detected by standard invasive angiogram corresponding to the event location. 55 In this scenario, cardiac CT may play an important diagnostic role by identifying non-stenotic culprit lesion with the above morphological features of vulnerability, in the clinical contest of embolic/spontaneous recanalization myocardial infarction. According to a recent subanalysis of the ROMICAT II trial population, a score derived from high-risk plaque features was emerged to be an independent predictor of ACS during the index hospitalization and was incremental to clinical variable and presence of obstructive ($50%) stenosis.…”